I am looking for a good, used Powermatic table saw, probably a 66. Does anyone know of a reference that helps date Powermatic saws by serial number? Does anyone know of a good source for tips on "good years", ie. saws from the 70's vs 90's etc. I have 3 phase and am scouring the auctions but want to have some idea of the age before I bid. Some are yellow, some are green. I'm sure that has some connection to age.